Healthcare companies were among the worst performing stocks Wednesday, with biotechnology sector-specific ETFs taking the brunt of the hit, after FDA Commissioner Scott Gottlieb unexpectedly resigned, casting a cloud over policy changes ahead.

On Wednesday, the Health Care Select Sector SPDR ETF (NYSEArca: XLV) declined 1.5% while the S&P 500 Health Care Index experienced one of its worst one-day sell-offs since January. Among the worst performing non-leveraged ETFs, the SPDR S&P Biotech ETF (NYSEArca: XBI) decreased 4.1%, ALPS Medical Breakthroughs ETF (NYSEArca: SBIO) retreated 4.9%, Loncar Cancer Immunotheraphy ETF (NasdaqGM: CNCR) dropped 4.3% and the iShares Nasdaq Biotechnology ETF (NASDAQGM: IBB), the largest biotech exchange traded fund by assets, fell 3.1%, with the major biotech-related ETFs testing their long-term support at the 200-day simple moving average.

The pullback in the healthcare segment was attributed to mounting concerns related to “Medicare for All” legislation, despite a string of biotechnology buyouts that helped bolster the sector, Bloomberg reports.

“You throw in the year-to-date performance within biotech and the medicare for all headlines (albeit viewed by most as noise and not viable) and the space feels pretty vulnerable,” Jefferies healthcare sector specialist Jared Holz told to Bloomberg News, adding that a resolution of the FDA issue should happen shortly which should ease “some fears and lessen the uncertainty the resignation has created.”

Salim Syed, senior biotech analyst at Mizuho Securities, said that Gottlieb represented a more “friendly FDA,” arguing he was “generally really liked by the biopharma investment community,” CNBC reports. “Finding somebody better than him, that’ll be hard.”

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Graham Parry, a research analyst at Merrill Lynch who covers the sector, also warned clients late Tuesday that Gottlieb’s resignation was a “net negative for innovative biopharma companies.”

Over the past year, Gottlieb, who previously served on the board of several drug companies and worked as an industry consultant, approved a record number of new and generic drugs.

“Gottlieb, in our view, as a healthcare policy expert, has been a key influence and architect, along with HHS secretary Alex Azar (former Pharma executive), of relatively innovator-friendly, evidence-based Trump administration healthcare policies and reforms laid out in its drug pricing blueprint last year,” Parry added.

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